As disclosed in a related-art document [1], which is listed below, indicators such as “precision,” “aveP,” and “recall” described below are known as an indicator indicating performance of an information estimation system.
                    precision        =                              count            ⁡                          (              L              )                                /          L                                    (        1        )                                aveP        =                              1            R                    ⁢                                    ∑                              1                ≤                i                ≤                L                                      ⁢                                          isrel                ⁡                                  (                                      s                    i                                    )                                            ·                                                count                  ⁡                                      (                    i                    )                                                  i                                                                        (        2        )                                recall        =                              count            ⁡                          (              L              )                                /          R                                    (        3        )            
In the equations (1)-(3), L represents the number of recommended items, R represents a total number of suitable items, i represents an i-th ranked recommended item, isrel(si) represents a degree of suitability of si for a user's interest, and count(i) represents the number of suitable items of top i-items in the ranking.
The “precision” indicates a ratio of items (count(L)) suitable for a user's preference occupied in a recommending list. “aveP” indicates an average value of “precision” of the items (isrel(Si)) suitable for the user's preference in consideration of the ranks. The “recall” indicates a ratio of the items suitable for the user's preference to the entire suitable items (R). By using the indicators such as precision, aveP, and recall, it is possible to measure the degree of suitability of the recommended result for the user's preference.